Tracked recreational vehicles for use on snow and winter terrain have been known for some time, and for nearly as long there has been a perceived need to provide for ways to use them on water, either as watercraft or for safety in travel over frozen bodies of water where there is a danger of breaking through the ice and submerging (see for example U.S. Pat. No. 3,646,904 to Lanning et al., which describes an early snowmobile with flotation and water drive means).
U.S. Pat. No. 6,595,812 to Haney solves the problem by providing a drive-in boat hull, into which a snowmobile may be inserted and sealed for use over water, the boat hull providing flotation, which leave the skis in place and provide for amphibious (water, snow and ice) operation of the conjoined vehicle. The skis are provided with additional surface area to act as forward steering elements while waterborne, and the track is used to provide propulsion in both water and over snow and ice. By attempting to convert to an amphibious vehicle, performance as a watercraft is compromised with a high-drag broad single hull and awkward steering components, the complexity of a series of water-tight seals, and the like.
U.S. Pat. No. 4,893,692 to Smith makes a snowmobile approaches the problem of safety when a rider breaks through ice and falls into the water, by including waterproof hull components and skis with pontoon-like flotation characteristics to provide buoyancy in the event of such an accident. This vehicle is not designed as a watercraft for recreational purposes, but rather as a snow craft with buoyancy for safety purposes.
U.S. Pat. No. 3,611,979 to Hebert discloses the replacement of mechanical suspension elements with a resilient flotation casing (bladder-like bag) disposed between two endless drive tracks to provide a small, buoyant amphibious vehicle for use over snow and ice, and water. This vehicle compromises suspension system performance for waterborne flotation, among other problems.
U.S. Pat. No. 3,646,904, as noted above, discloses a set of two pontoons with mounting arrangements onto which a partially disassembled snowmobile can be bolted, and which can attach the pontoons' included propeller and rudder systems to the engine and operator control systems, respectively, of the snowmobile; this provides a pleasure watercraft powered by the snowmobile's engine, but requires removal of the snowmobile's track, and complex connections of the engine and steering controls to additional propeller and rudder systems on the pontoons.
U.S. Pat. No. 6,062,156 to Radke et al. discloses a snowmobile—powered watercraft with floats for skis and a massive bolt-on U-shaped rear float which surrounds the snowmobile, enclosing its rear-end. The rear enclosure (the joining part of the “U” shaped hill, behind the vehicle between the two side parts of the hull, one each side of the vehicle) provides an adjustable trim tab, added bulk, and unnecessary weight, manufacturing complexity, drag, and a single point of failure.